Radio Frequency (RF) coverage is an important consideration in the deployment of Radio Frequency Identification (RFID) systems. One factor that impairs RF coverage are the nulls that result from destructive interference caused by multipath fading. On the other hand, multipath propagation can also result in constructive interference, which can improve RF coverage and the range of an RFID reader.
RFID readers that employ beam steering techniques using phase array antennas typically have better RF coverage than RFID readers that use traditional antennas due to the phase array antennas' ability to steer a beam and thereby mitigate fading due to multipath. Correspondingly, the better the directivity of an antenna, the better the ability of the antenna to mitigate fading. However, a large antenna is required in order to achieve high directivity, which may pose mounting problems and may be undesirable for an RFID reader, where the smaller the reader the better.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions and/or relative positioning of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention. It will further be appreciated that certain actions and/or steps may be described or depicted in a particular order of occurrence while those skilled in the art will understand that such specificity with respect to sequence is not actually required. Those skilled in the art will further recognize that references to specific implementation embodiments such as “circuitry” may equally be accomplished via replacement with software instruction executions either on general purpose computing apparatus (e.g., CPU) or specialized processing apparatus (e.g., DSP). It will also be understood that the terms and expressions used herein have the ordinary technical meaning as is accorded to such terms and expressions by persons skilled in the technical field as set forth above except where different specific meanings have otherwise been set forth herein.